The increased use of microprocessor based diagnostic test equipment in the automotive repair field has provided increased operator productivity in both engine performance testing and repair. The newer test equipment not only allows for more precise measurement of the various engine performance criteria, but it performs these measurements more quickly. In those applications in which the measured data is used for performance acceptance, or in compiling a performance history, data display is not necessarily of concern. However, the quality and format of the data display are important in those applications where the data must be immediately evaluated by the human operator, e.g. those interactive applications in which the test equipment is used to provide the resulting instantaneous performance indication of a repair or adjustment made by the operator on the engine. In other words, those applications in which the equipment is "in the loop" together with the operator performing the adjustment.
Although the equipment data acquisition speed is important, in this interactive mode the limiting factor is the reaction time, or "interpretation speed" required by the operator. That is, the speed with which the operator may read and understand the meaning of the sensed data and reach a conclusion. The prior art use of oscilloscope displays and separate meter indications (analog and digital) require the operator to make interpretative decisions, e.g. the location of the measurement indicator on the scale, or the "relative value" of the single measurement readout absent corresponding readouts of the other performance measurements criteria (relative power contribution), or the need to remember oscilloscope patterns.